Problem with servo's?

[Greg Orders]

Hi Guy's thought I'd try and pick someones brains on here. I have a signstech 1612SP 130watt laser cutter with panasonic MDHT2510E servo drivers, the software is Laserwork version5.21. My problem is that when I raster engrave it works fine until I try to cut around the engraved area it cuts off centre to engraving? I also have found that I have to engrave in x_unilaterilism as if I try to engrave in X_swing it ends up cutting a double figure as in it has a shadow round outlines. Iam assuming it is something in the setup of the servo controllers as the other machine is the same but uses steppers and it works fine on cutting and engraveing . Thanks in advance for any help you guy's can give me.

Regards
Greg

[Greg Orders]

Just to show everyone the problem in more detail I have uploaded a photo which shows the problem. I think it is in the setup of the Panasonic servo controllers.

[Gary Hair]

That looks like pretty severe backlash, not necessarily a problem with the servos but rather a mechanical problem with the machine. I would contact the mfg and ask them how to reduce the backlash and/or how to account for it in the setup.

Gary

[Greg Orders]

Hi Gary thanks for that, but it is not backlash as I can manually move the carrage to any position on the table then press run and it will cut in exactley the same spot again and again. The controller is an RDLC-320A running Laserworks ver 5.21 and there is very little you can adjust in both user and manafactures settings. I have a copy of Panaterm which allows me to directly connect to each servo driver and adjust settings, but there is aroound 100 different settings to play with and some of them are extreme. As this is a Signstech laser machine I haven't had any luck with them as they responded saying the laser was out of focus and needed adjustment!! Een I could tell thats not the problem. Might be new to laser cutters but I have built and been using my own CNC rounter a Lionclaw50b for around 3 years now using mach3 so I do have a fair idea on how the systems work. my biggest problem is learning how to setup the servo drives correctley as the guy's in China obviously don't as the machine was tested by them before being sent supposedley. By the way if you engrave using unilaterism instead of x swing it works ok but will cut in wrong position, 1/2 of the error and this error occurs on both axis ie x_swing or y_swing will give exact same result. So thanks again but I despute it being backlash.

[Rodne Gold]

You can easily change the machine to steppers if it becomes real problematic to sort out the servo's (are they open or closed loop?)..all you need are the stepper drivers and motors , prolly cost round $300 at worst.

[matthew knott]

I remember when my old company changed from steppers to areotech servos. it was a nightmare, tuning them was a real pain, it seemed to be a black art getting the servo loop tight, especially hard if you had something with a flexible element in the drive train (like rubber belt or coupling). They came with some horrible MMI software that had an autotune function, but it never worked. I would try on CNC forums as its not really a laser related problem, bound to be an expert around, look here http://support.motioneng.com/downloads-notes/tuning/default.htm for the basics of PID control, Im a big fan of stepper motors, slow but ultra simple!!

[Greg Orders]

252937Bit of an update manufacture reckons it is belt flex!! So I sent them another pic with more detail to show exactley why I argue that it is software and timming related see for yourself. Prety certain signstech have no iea how to fix it so I will persevere myself and rectify the problem.

[Richard Rumancik]

. . . I also have found that I have to engrave in x_unilaterilism as if I try to engrave in X_swing it ends up cutting a double figure as in it has a shadow round outlines. . . .

I'm sure you are getting a bit frustrated as I see your original post was in December and you did not get any responses - your original question (without a photo) didn't really give people much to go on.

When you say "x_unilateralism" I assume this is some kind of translation to mean that it is marking only on the left-to-right pass and does not fire on the return stroke. And that "x_swing" means that it is firing on both passes . . . correct me if I am wrong here.

So what is happening is that on the "return pass" the laser is firing early (relative to first pass), causing the right edge and left edge of the pattern to be out of alignment with each other. This is not an uncommon occurance with lasers, and the normal solution is to have a function in the driver/software to adjust the timing so that the edges are justified. It would delay the firing of the laser in both directions so that the lines converge with a common boundary. Then the vector box would enclose them properly.

Some laser manufacturers call this "tuning" but there is probably not a universal term for it. I think you need to search through the software and driver to see if you can find the function. I don't know how they could do without such a function . . . maybe your contact did not quite understand what you meant. Are you working through a distributor or the manufacturer? Surely the manufacturer's engineers would know right away what was going on. I would not expect that this "tuning" would be done in hardware but I suppose it could be done with a potentiometer - a software/firmware solution is a lot nicer. Either way, there should be some way to do it.

I'm trying to decide if a bad tickle setting could cause this situation but I'm not really sure. Since the laser seems to be firing prematurely in both directions it might be possible to get better convergence by reducing the tickle setting (assuming you have one.)

So this machine can raster in the y direction as well as the x? That is an unusual option. Most laser manufacturers don't allow for this as you would have to move the whole gantry, which can't be accelerated at high speed. I assume that y-rastering is very slow.

[Kees Soeters]

Looking at the last photo.. i can hardly believe you will suffer beltstretch at 10mm/sec. Not even the slow 300mm/sec should stretch your belt. (the square in one of the first photo's don't shows any overshoots)
Have you checked the trigger-edge coming from the controller?
Kees

[Rodne Gold]

There is a backlash adjustment that needs to be set , It's normally a software setting not a hardware thing , it might not be called backlash ,but might be called bidirectional compensation or something like that , you need to set it at a few speeds as it changes with speed , you need to set it so all those parallel lines you engrave line up at the various speeds, normally the software extrapolates for speeds between those you have tested and set.

[Greg Orders]

Thanks Guy's Rodne tried backlash at different values and the gap between the letters increases as the backlash setting is increased. ie the 2 A's etc end up further apart not as you would expect them to be closer together so backlash is not the problem. I need to be able to adjust the firing time of the laser which iam pretty sure you can't physicaly do in laserworks 5.021. My other option is to make a microchip board and program it to delay the laser as required. Although I can do this shouldn't have to as the machine should do what they said it would do. Thanks again.

[Richard Rumancik]

Well, adjusting the backlash made it move - just the wrong way. What value was it when you started? What is the range of settings the user interface will accept? Will it allow a negative value? I don't know the hardware at all, just trying to brainstorm what might work.

The Panaterm setup is a bit imtimidating for a casual user - (I took a quick look at the manual) - probably you need someone quite familiar with it to determine if there is a parameter in there you can tweak. In reality the Panaterm interface should be done behind the scenes by the controller and firmware, not by the user. Are you sure the Panaterm has been reset back to the factory settings after your experiments?

I think the RDLC-320A is used in quite a few different Chinese machines so maybe keep hunting to see if you can find a user who might be able to shed some light on it.

Adding your own circuit to delay the firing might work but it shouldn't be necessary to re-engineer this design. I think if you did it you might find more "gotchas" - you probably would need the delay to be in the circuit for rastering, but out for vectoring. Some people must be making this controller work without having to redesign it . . .

[Rodne Gold]

The backlash does take negative values and it isnt really a physical backlash compensation, it controls where the laser fires on the backstroke. Try - values.

[Greg Orders]

The backlash does take negative values and it isn't really a physical backlash compensation, it controls where the laser fires on the backstroke. Try - values.
Hi Rodne sorry when negative value's entered software auto resets to 0.00 so no it won't accept neg value's. I have found after playing round today that in the panaterm servo controllers there is a feed forward gain setting that was set at .54ms, I changed this to 0 and the error at 300mm/sec is now at the error of 10mm/sec, so a bit more fine tuning of the servo's and I will solve the problem. Just a petty the guy's who sell the stuff can't back up what they sell and if anyone on here has dealt with the company that makes the RDLC-320 software and got any assistance from them let me know cause when I tried contacting them they read my email and didn't bother answering. Thanks again Guy's but looks like I will get it right after all cheers.

[Rodne Gold]

you can download the rdlc320 users manual from
https://www.google.co.za/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CFMQFjAC&url=http%3A%2F%2Fen.rd-acs.com%2FPrivate%2FFiles%2FUsers%2520Manual%2520o f%2520RDLC320%2520Control%2520System.doc&ei=DXULUcy5Ksia1AXB34HwCw&usg=AFQjCNGwW-0R7SfLy9EA-2qVMaClknakoQ&sig2=hApGsALfXrTShilpx0gE1Q&bvm=bv.41867550,d.d2k